I had XP on my computer. I reformated it and installed windows 7. Now when I push the button to switch it on it keeps rebooting after about 4 to 5 seconds. It reboots between 3 to 5 times then switches off. The computer doesn't even comunicate with the monitor, I get no images at all on the screen. So I cant tell if I am getting any error messages. I have tried taking the power cable out off the back and holding the power button in for about 5 seconds to discharge the power unit but that makes no difference at all.